Form, fill and seal industrial bag machine

ABSTRACT

Side gusseted industrial bags are continuously (or intermittently) formed from continuous web materials, and simultaneously filled and sealed in one fast operation by the method and apparatus of this invention. The various features of the invention include a tube former which wraps the web about a shaped filling mandrel most preferably with the assistance of an air bearing, registration and tension controls to accurately maintain the register of the web in relationship to printed blocks or indicia; evacuation steps to neatly gusset the bag with or without mechanical assistance, to tighten the bag firmly about the product, and to continuously wash the inside welding surfaces thereof with a cleansing high velocity air stream to thereby retain such surfaces in a more virgin or noncontaminated welding condition; filling steps that are practiced to provide a free margin of material at the top of the bag to complement the welding and gusseting steps; and hot gas welding and chilling techniques that can provide tough welds or seals with high repeatability, and which are able to withstand the shock or weight of the product load with sufficient immediacy to enable fast production cycles.

United States Patent Greenawalt et al.

[ 1 Dec. 16, 1975 FORM, FILL AND SEAL INDUSTRIAL BAG MACHINE [75] Inventors: Eddie Lee Greenawalt; Lorenzo Dow Geren, both of Lake Jackson, Tex.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

[22] Filed: Apr. 15, 1974 [21] Appl. No.: 460,864

Related US. Application Data [63] Continuation-in-part of Ser. No. 347,923, April 4,

1973, abandoned.

[52] US. Cl. 53/182; 53/373; 156/497 [51] Int. Cl. B6513 9/08 [58] Field of Search... 53/179, 180 M, 182, 182 M, 53/183, 373; 156/497, 498, 510, 515; 219/374 [56] References Cited UNITED STATES PATENTS 2,837,883 6/1958 Bracey 53/182 M 3,195,285 7/1965 Toss 53/182 X 3,381,441 5/1968 Condo et al.... 53/182 M 3,529,400 9/1970 Takagaki 53/373 X 3,538,676 11/1970 Runo et al 53/182 M 3,775,222 ll/1973 Aspin et a1 .1 156/497 {2 ll l-i 52 P ill 5 ia'.

l 1Ill1 Primary Examiner-Robert L. Spruill Attorney, Agent, or Firm--Burke M. Halldorson Side gusseted industrial bags are continuously (or intermittently) formed from continuous web materials, and simultaneously filled and sealed in one fast operation by the method and apparatus of this invention. The various features of the invention include a tube former which wraps the web about a shaped filling mandrel most preferably with the assistance of an air bearing, registration and tension controls to accurately maintain the register of the web in relationship to printed blocks or indicia; evacuation steps to neatly gusset the bag with or without mechanical assistance, to tighten the bag firmly about the product, and to continuously wash the inside welding surfaces thereof with a cleansing high velocity air stream to thereby retain such surfaces in a more virgin or noncontaminated welding condition; filling steps that are practiced to provide afree margin of material at the top of the bag to complement the welding and gusseting steps; and hot gas welding and chilling techniques that can provide tough welds or seals with high repeatability, and which are able to withstand the shock or weight of the product load with sufficient immediacy to enable fast production cycles.

ABSTRACT 32 Claims, 34 Drawing Figures Sheet 1 of 12 3,925,963

U.S. Patent Dec. 16, 1975 U.S. Patent Dec. 16, 1975 Sheet 2 of 12 3,925,963

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U.S. Patent Dec. 16, 1975 lljjlillllllllllll'l'gfn Sheet 4 of 12 3,925,963

US. Patent Dec. 16,1975 Sheet70f 12 3,925,963

8% @WM WWW US. Patent Dec. 16,1975 Sheet 12 of 12 3,925,963

FORM, FILL AND SEAL INDUSTRIAL BAG MACHINE CROSS-REFERENCE TO RELATED APPLICATION The present application is a continuation-in-part of our copending application Ser. No. 347,923 filed Apr. 4, 1973, and now abandoned BACKGROUND OF THE INVENTION Any bag that is 25 or more pounds (11.35 kgs) in weight is normally classed as a heavy duty or industrial size bag. This class bag enjoys tremendous packaging and shipping usage throughout the world. Nearly all or all of the industrial bags produced commercially prior to this invention have been based on a preformed or pre-made bag construction.

It would amount to very meaningful cost savings, however, if heavy duty bags couldbe produced on a fast in-line operation, 'based on a form, fill and seal concept. The prior art, however, has not provided the technical progress that is needed in order to make a sure and widespread transition from the preformed, to an in-line formed, filled, and sealed industrial bag.

Perhaps the most crucial problem, if viable technical progress is to be made, is the need for improved methods and apparatus for forming the bag seals or welds. Achieving good sealing results has been a past problem even as regards preformed plastic bags which require only a minimum of sealing after filling, the majority of the seals having been pre-made by the bag manufacturer under controllable, essentially stress free, ideal conditions. For example, in the March 1968 issue of Food Engineering, it is reported at page 116 that: Bag damage with the all-plastic bag was considerable due to failure of the heatsealed closure. The closure would open in transit, and that would be that. This isn't a product that can be recoopered."

The welding of heavy duty form, fill, and seal industrial bags is understandably even more touchy, since the process does not have the benefit of ideal bag manufacturing conditions. There is not the luxury of being able to form and cure the seals or'welds in a stress free environment. Moreover, the fresh welds must accept the stress and distortions of the product load almost immediately, and must be formed with extremely high repeatability and good results for commercial acceptance. Still further, the welding technique must be able to securely weld through heavy gusseted areas if it is to achieve true success. A gusseted bag is relatively square and provides a stable pallet load, and it is essential that an industrial bag have this quality if it is to be an optimum bag. For illustrative example, a bag of 10 mil wall thickness would be 40 mils thick in the gusseted areas, 30 mils thick along the overlap or longitudinal seal, and 20 mils thick in other areas. The welding technique must accommodate such wide variances in thickness along a single weld line. Particularly, it must form a tough weld even at the points of abrupt thickness change, and without causing delineated lines of pronounced weakness or thinning.

The method and apparatus for properly side gusseting the formed, filled and sealed industrial bags is another problem area. For example, in a form, fill and seal process, the side gussets must be formed after the bag has been influenced by the distortion and weight of the product load, whereas, in a preformed bag, the side gussets can be neatly tucked in and secured under far more compatible conditions. Particularly if a form, fill,

and seal industrial bag is to be optimally suited for commercial use, i.e., palletizing, there must be provisions for including functionally adequate side gussets in the ultimate bag structure.

Still further, the desired method and apparatus for producing an acceptable form, fill and seal industrial bag, should advantageously provide for flexibility in the materials from which the bag can be formed. The ultimate performance of an industrial bag, of course, depends on the materials from which it is manufactured. It is extremely desirable, for example, that in some uses, the industrial bag be provided with multiple plies of material to better absorb the expected handling abuses. Most desirably, therefore, the operation should be, sufficiently flexible to permit the usage of webs of multiple plies of material, together with tough scrim layers such as of fabric, nylon, rayon, and the like, that give the bag improved overall integrity. A multi-layer bag is generally felt to be tougher than a single ply bag of equivalent thickness, and the scrim layers can add considerable abuse resistance to the bag.

As yet another factor to be dealt with, a prospective form, fill, and seal method and apparatus for industrial bags should, for optimum versatility, expediently prepare the bag for a post-shrinkage step. This flexibility will permit the bag to be tightly shrunk about the product so that it retains a firm, tight character through a normal or even extended use period.

Accordingly, it is the primary objective of this invention to provide an apparatus and method suitable for in-line forming, filling, and sealing of industrial size bags.

It is particularly among the objectives of this invention to accomplish the primary objective with a maximum of finesse and flexibility, whereby the method and apparatus are advantageously designed to:

i. form exceedingly tough welds with a very high degree of repeatability, that can withstand the abuses of commercial handling with an acceptably low frequency of failure, and, that can withstand the weight of the product load with sufficient immediacy to enable fast production rates;

ii. permit manufacture of side gusseted bags with optimum palletizing and handling characteristics, and wherein the welding procedure is able to weld through and secure the gussets strongly in the bag structure;

iii. handle excessively dusty products of the type that normally give problems through contamination of welding surfaces;

' iv. optimize the palletizing and handling characteristics of the bag and minimize material usage, by forming a tight, firm bag about the product;

v. automatically precondition the bag for a postshrinkage step;

vi. achieve finesse in holding and maintaining proper registration so that the bags can be produced with accurate registration of printed blocks and indicia thereon; and

vii. fill the bags in a manner that complements the welding and gusseting of the bag with repeatedly good results, and that facilitates the performance of these objectives at commercially acceptable manufacturing speeds.

Other objectives, aspects, and advantages of the invention will in part be pointed out in, and in part apparent from, the following description considered together with the accompanying drawings, in which:

FIG. 1 is a side elevational view illustrating apparatus for forming, filling, and sealing industrial class bags in accordance with the general teachings and principles hereof, certain parts of the apparatus being shown in this view in generally abbreviated or schematic detail;

FIGS. 2 through 4 are views like FIG. 1, which are used to illustrate the process of the apparatus thereof, particularly in the sense of showing progressive stages in the filling cycle of such apparatus;

FIGS. 5 through 7 are cross-sectional views through FIGS. 2 through 4, respectively, taken along reference lines 5-5, 6-6, and 7-7, respectively;

FIG. 8 is a plan view which illustrates in somewhat more thorough detail, the preferred embodiment of the unwind assembly from which a continuous web is fed to form the bags, and also partially shows the drag inducing or applying unit associated therewith for automatically varying and controlling the tension on the web;

FIG. 9 is essentially an elevational view that illustrates the drag applying unit as viewed along reference line 9-9 of FIG. 8;

FIG. 10 is a side elevational view which illustrates in somewhat more thorough detail, the preferred embodiments of the filling mandrel, tube former, and vertical seam welder of the apparatus of FIG. 1;

FIG. 1 1 is a front elevational view of the apparatus as shown in FIG. 10, except with the vertical seam welder having been broken away and not illustrated in this view;

FIG. 12 is a cross-sectional view taken along reference line 12-12 of FIG. 10, and essentially comprises a plan view of the apparatus as shown in FIG. 10;

FIG. 13 is a plan view of the vertical seam welder of FIG. 10;

FIG. 14 is a cross-sectional view of the vertical seam welder of FIG. 13, taken along reference line 14-14 thereof;

FIG. 15 is an enlarged, partial view showing the air bearing and adjusting clamp of the tube former;

FIG. 16 illustrates the vertical weld formed in the bag in a condition immediately after it passes the vertical seam welder and associated chilling head; and FIG. 17 shows the same weld after having been subjected to the shock of product load, whereby essentially all wrinkles are removed from the weld and an invisible or near invisible weld line is achieved;

FIG. 18 is a plan view wich illustrates the apparatus of FIG. 1 in more thorough detail, this view looking down into the bag sizing cage of the apparatus;

FIG. 19 is a cross-sectional view taken along reference line 19-19 of FIG. 18, and illustrates particularly the floating pressure plate employed to control the clamping pressure in the bag sizing cage;

FIGS. 20, 21 and 22 are front elevational, plan, and end views, respectively, which illustrate in more thorough detail, the preferred embodiment of one of the co-acting sealing heads of the apparatus of FIG. 1, a portion of FIG. 21 being broken away to reveal the moveable cutter head carried by this sealing head;

FIG. 23 is a cross-sectional view through FIG. 21, taken along reference line 23-23, thereof; FIGS. 24 and 25 are front elevational and plan views, respectively, which illustrate in more thorough detail, the preferred embodiment of the opposite co-acting sealing head of the apparatus of F IG. 1, a portion of FIG. 24 being broken away particularly to illustrate the detail of the hot and cold gas valves included in the design of this sealing head;

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FIG. 26 is a cross-sectional view through FIG. 24, taken along reference line 26-26, thereof;

FIG. 27 is a partial side elevational view particularly illustrating the co-acting sealing heads at a moment just prior to their engagement to form the end welds of the bag in accordance with the FIG. 1 apparatus and process thereof;

FIG. 28 is a cross-sectional view showing the engaged co-acting sealing heads at a moment in the welding cycle when a hot gas stream is being applied thereby to form the end welds on the bags;

FIG. 29 is a cross-sectional view partially through FIG. 18, taken along reference line 29-29, thereof, and particularly illustrates the preferred assembly for delivering hot welding gas to the sealing heads;

FIG. 30 is a cross-sectional view through FIG. 29, as taken along reference line 30-30, thereof;

FIG. 31 is a cross-sectional view through FIG. 18, taken along reference line 31-31, thereof, and particularly illustrates the preferred assembly for delivering cooling gas to the sealing heads, together with the structure of one of the two revolving gusseting arms for providing mechanical assistance in side gusseting bags made according to the FIG. 1 apparatus;

FIG. 32 is a cross-sectional view through FIG. 31 as taken along reference line 32-32, thereof;

FIG. 33 is an enlarged partial view which illustrates a modification to the filling mandrel designed to create a high velocity stream to continuously wash over the inside surfaces of the bag;

FIG. 34 is a cross-sectional view through FIG. 33 as taken along reference line 34-34 thereof;

Intent Clause Although the following disclosure offered for public dissemination is detailed to ensure adequacy and aid understanding, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how it may later be distinguished by variations in form or additions of further improvements. The claims at the end hereof are intended as the chief aid toward this purpose, as it is these that meet the requirement of pointing out the parts, improvements, or combinations in which the inventive concepts are found.

Description of the Illustrated Embodiments A general teaching of the illustrated apparatus and process hereof is described in relation to FIGS. 1 through 7. Referring first to FIG. 1, apparatus generally designated at 10, includes an unwind assembly 12 which rotatably mounts a rolled up web 14 of single or multi-ply, thermally sealable material. The web is continuously drawn off the unwind assembly at a constant rate by means to be described and under tension which is controlled automatically by a drag applying unit 16. The web is initially directed generally upwardly about idler feed rolls 18 and 20 to an idler approach roll 22. The approach roll feeds the web at a controlled angle to a tube former 24, from whence it is drawn downwardly therethrough. The tube former continuously wraps and rolls the web about a hollow filling mandrel 26 to provide a continuous vertical tube having its marginal or longitudinal edges overlapped. The overlapped edges are continuously welded together by a hot gas, vertical seam welder 28. The fresh weld or seal is generally immediately partially cured by an impinging cooling gas supplied through a chilling head 30 mounted underneath seam welder 28.

The tube is then drawn through a bag sizing cage 32. The sizing cage includes opposed, continuous chain assemblies or vertical conveyors 34 and 36, which are spaced to define a vertical cavity 38 through which the tube passes. The conveyors have mounted thereto and convey a continuous series of slats 40 which define the effective width of cavity 38; and also mount and convey a predetermined number of co-acting sealing heads 42 and 44, respectively. The sealing heads regularly come together to mate at a point below the lower terminating end of the filling mandrel, and grasp the tubing therebetween, each time forming a temporary bottom, while continuously drawing or pulling the tube downwardly to provide successive product receiving spaces in the tube. Simultaneously the sealing heads transversely cut and weld the tubing at regular intervals and cool the welds, before disengaging and being returned to repeat this cycle. The bags as they are manufactured, are deposited onto a horizontal conveyor belt 56 operating underneath the sizing cage.

The bag filling mandrel 26 is arranged generally concentrically within, and extends axially both above and below the tube former. In the region of the tube former and thereabove, the filling mandrel is of cylindrical cross-sectional shape. Beginning near the lower extent of the tube former, the filling mandrel gradually changes to an ultimate configuration at its terminating lower end portion 46, as seen in FIGS. 5-7 (see also FIGS. -12). The end portion 46 comprises opposed, generally flat sidewalls 48 and 50 connected by opposed formed V-shaped end sections 52 and 54. This transformation in shape is to assist gusseting the tube in a manner as will be described. Also to this purpose, end portion 46 is peripherally bounded by horizontal restraining elements or means comprising horizontal restraining bars 60 and 62, extending in close parallel relationship with sidewalls 48 and 50, respectively; and gusseting rollers 64 and 66 disposed partially within the inwardly formed end sections 52 and 54, respectively.

A product holder chamber 68 is affixed to the top of the filling mandrel through means of flanged ends 70 and 72 in these pieces, respectively. The holding chamber communicates with the filling mandrel through a slide gate 74 operated through an air cylinder 76. The holding chamber contains a dump bucket 78, which is suspended by attachment to the arms 80 (only one showing) of a weighing scale 82. The dump bucket is released by a hinged bottom trap door 84, through an air cylinder 86 and bracket connection 88. An electronically controlled surge hopper, shown partially at 90, or another suitable product introducing means, is connected into the top of the holding chamber. The holding chamber is adapted to be evacuated by a high capacity, low vacuum evacuation fan 92. The filling mandrel is adapted to be evacuated, independently of the holding chamber, by a high vacuum, low capacity evacuation fan 94.

The repetitive filling cycle of apparatus 10 is initiated by the transfer of product from the surge hopper into the dumping bucket. The scale 82 automatically weighs the product and at the proper moment electronically signals the surge hopper to gate closed. The weighed product load is then dumped from the bucket onto slide gate 74 where it remains for a brief holding interval. During this interval, the product load is subjected to an evacuation step drawn through fan 92. Preferably both the fans 92 and 94 operate continuously to minimize cycle times. The evacuation of the holding chamber serves the purpose of removing entrained air from the product load. In order to optimize this end result, the holding chamber is preferably evacuated to the maximum extent compatible with the limits of subsequent bag filling steps. These limits are determined mostly by the kinetic energy available from dropping the product load from the elevation of the slide gate. The product load, briefly, must have. sufficient energy to quickly shock or pop the tube open and be received therein in proper timing to the mating of the sealing heads, as will be explained more fully hereinafter.

The remainder of the filling cycle is shown progressively in FIGS. 2 through 5. In the FIG. 2 illustration, the product load is shown deposited on the slide gate at the instant just prior to dumping. The holding chamber and the filling mandrel are both under internal evacuation. The degree of vacuum is greater in the filling mandrel due to the relatively higher vacuum draw capability of fan 94. The tube at this instant is sucked tightly against the sides of the filling mandrel, and is collapsed tightly upon itself therebelow due to the inward bearing of atmospheric pressure.

FIG. 3 illustrates the filling cycle after opening slide gate 74, and initial entry of the product load into the tube. An instant after the slide gate opens, the lower vacuum maintained in the holding chamber tends to dominate over the filling mandrel to partially relieve the vacuum induced stress on the tube. The stress is momentarily relieved at least sufficiently for the energy of the product load to open the collapsed tube, and for the product load to be received quickly therewithin. The evacuation fan 94 is designated as a low capacity fan in the sense that this fan does not have the capacity to recover fast enough after the slide gate opens, to prevent the necessary degree of relief on the tube. The energy of the product load is essentially the energy of the elevational drop of the load, as influenced by the downward sucking effect applied to the product load by the unbalanced vacuum pressures in the filling mandrel and holding chamber at the instant the slide gate is opened. This energy must overcome the pressures bearing inwardly on the tube, and most optimally distends the tube sufficiently to fully accept the product load before the entirety of the bag has passed the filling mandrel. The mandrel will in this manner shield the upper welding surfaces of the bag from direct engagement with the product. Inherently also, the product load is momentarily packed toward the bottom of the bag, in a position to be forced upwardly by the squeezing action of the sizing cage, as will be explained more fully hereinafter. The timing of this latter step provides the momentary condition of a margin of free space at the top of the bag, thereby lessening any chance of an interference between the product load and the sealing heads. By the same token, the bag is made more receptive to the formation of neat appearing side gussets therein by a procedure to be described. The consequence that must be avoided, in any event, is backup of the product load into the fillingmandrel to any extent as would cause a delayed filling action, whereby product would dribble from the mandrel, and become interposed between the sealing heads at the instant the same close or clamp across the tube.

The filling cycle is shown toward its last stages in FIG. 4. The sealing heads 42 and 44 are ready to engage underneath the mandrel to form the top end of the bag of this discussion, and simultaneously the bottom end of the bag next to be filled. The slide gate 74 is closed, and a new filling cycle is already in process.

With the gate 74 in the closed position the high vacuum fan 94 dominates over the filling mandrel to evacuate preferably as much air from the bag as is possible before the sealing heads close. The object is to tighten and firm up the bag to impart acceptable, and preferably optimum palletizing and handling characteristics thereto. Moreover, a firm bag uses less material, and the product load is in a sense densified by the evacuation steps so that it requires less packaging space. Air is more quickly removed from the top of the bag up to a certain depth into the product. However, because of an inherent pressure drop through the product, the removal of entrapped and entrained air from the bottom of the bag is hampered. The first vacuum stage applied in the holding chamber, therefore, preconditions the product to better achieve the sought after objectives, under the conditions of fast, ecnomical cycle times.

Simultaneously, in controlled relationship with the timing or closing of the sealing heads, the sizing cage is acting to urge the product upwardly into the top portion of the bag. The sizing cage, overall, causes the product to flow and redistribute more evenly within the bag to give better shape and size uniformity thereto, and to negate internal void areas. The width of the sizing cage and its position is necessarily balanced with the various factors controlling the upward flow of the product, in order that this step is compatible with the movement and clamping of the sealing heads.

The evacuation procedure described above is also used to form neat, shape imparting gussets to the bag simultaneously with its formation. Further on herein, it will be described how this same step can be employed, in a modified practice hereof, to wash air over the inside surfaces of the tube, to avoid weld or seal contamination by product dust when such is a problem.

However, referring specifically to the formation of the gussets, this procedure is depicted in FIGS. -7. These figures are tied in time to FIGS. 2-4, respectively, to which they relate as cross-sectional views. In FIG. 5, the tube is in a condition where it is pulled by vacuum force tightly and flatly against the lower terminating end portion 46 of the mandrel, imparting thereto a relatively neat gusseted configuration having essentially inwardly collapsed or inwardly tucked opposed side portions as will ultimately comprise the gusset structure of the bag.

The subsequent shock of the dumped product load momentarily pulls the tube away from the mandrel as shown in FIG. 6. The memory of the gusseted shape, however, is retained inthe tube by means of peripheral restraint applied to the tube through restraining bars 60 and 62, cooperatively with gusseting rollers 64 and 66. The memory permits or encourages the gussets to properly and neatly reform after each dump, as the tube recovers and is sucked back tightly against the fillig mandrel, as seen in FIG. 7. In the preferred embodiment the shaped mandrel, with the assistance of the draw on the tube, thereby extends the gusseted structure into the area of the sealing heads 42 and 44 which permanently weld the gussets into the bag as it is formed.

The gusset structure, added to the bag by practice of the above cooperating restraining and vacuumizing steps, serves to square-up the bag giving it even better appearance, together with yet even further improved stackability or ability to be palletized. Despite the fact M'l hllllullllllwmmm that the gusset structure is permanently formed only gussets are surprisingly neat and strong due to the manner in which the bottom and top welds are formed securing the gussets. The welding technique is described in some depth hereinafter. As a general matter, however, the sealing heads first cut the tube. The cut edges are then bathed in a directionally controlled stream of hot air or other gas, through a welding cycle shown in FIG. 1, after which the edges are bathed with cooler air for a short period as also denoted in the same FIG. 1. No mechanical pressures are applied to the seal such as would cause delineated lines of thinning or objectionable preferential rupture lines. The welding technique is particularly able to accommodate welding across varying numbers of plies of material, as is the case with a gusseted tube, and form a strong weld at every interface.

Unwind Assembly and Drag Applying Unit The unwind assembly 12 and drag applying unit 16 are shown in more complete detail in FIGS. 8 and 9. The rolled up web 14 is rotatably carried on opposed plugs or collets and 102 which insert onto the opposite ends of the core of the roll. The plug 100 is freely rotatable on the end of a shaft 104 of a footed air cylinder 106, which is, in turn, fastened to a fixed horizontal mounting 108. The air cylinder moves plug 100 in and out for changing rolls, and the pressure of the plug against the roll is determined by regulating the pressure to the air cylinder. The opposite plug 102 is attached to the end of a horizontal shaft 110. The shaft is journably carried for free rotation by pillow bearings 112 secured to a fixed mounting 114. One or more annular spacers l 16 are adapted to be removably affixed to a collar 118 on the back of plug 102. The removal or addition of spacers allows the operator to precisely align the center line of the web with the center line of the tube former for accurate web feed to the tube former.

A pump 120, which is part of the drag applying unit, operates off shaft 110 by means of a chain and sprocket connection 122 therewith. Unit 16 is a closed system including a fluid reservoir 124 which is elevated above the pump (see FIG. 9). The reservoir with the assistance of a bracket 126, and the pump through a flanged end 128, are commonly attached to a fixed vertical plate which extends off fixed mounting 114. An inflow pipe 132 communicates between the bottom of the reservoir and the pump, and an outflow or discharge pipe 134 between the pump and a 4-way solenoid valve 136, which is affixed to the top of the reservoir through a mounting piece 138. The solenoid valve, in turn, communicates with the reservoir through a pair of variable restrictor valves and 142. Fluid is continuously fed through the inflow pipe to the pump, and the discharge is returned to the reservoir via one or the other of the restrictor valves, depending on the valving position of solenoid valve 136. The restrictor valves can each be needle valve assemblies which are adjusted to provide two settings. In one setting, the pump is required to work comparatively harder to return the fluid to the reservoir than at the other setting. This determines the drag applied to the unwind assembly thus giving variable tension control over the web, i.e., comparatively low or 'high tension depending at any certain time through which restrictor valve the outflow from pump 120 is being diverted by solenoid valve 136.

Web Registration Control The drag applying unit 16 is designed to automatically maintain the proper registration of printed web material. Unit 16 works in cooperation with three monitoring units or sensors, preferably electric eyes. One such electric eye 144 is placed in the sizing cage and records the event of each passage of sealing heads 42, through an offset tab 146, mounted to each head, and which breaks the circuit of this eye (see FIGS. 1 and 24). Reading this event established a point that never varies, i.e., known point. Electric eye 144 dominates second and third spaced apart electric eyes 148 and 150 positioned to read printed marks on the web as it comes off the roll.

Each time eye 144 reads the known point, it signals eyes 148 and 150 to look for a mark. If the mark is at some point between the eyes, no response is made since the web is within the registration tolerances. If the eye 150 nearest the tube former reads the mark, this indicates that the web is being over-stretched. This event signals the solenoid valve 136 to switch over to the low restrictor valve automatically lessening the tension on the web to keep the same in proper register. Conversely, if the eye 148 farthest from the tube former reads the mark, the web is being under-stretched to maintain registration, and the solenoid valve is signaled to switch the outflow of the pump through the high restrictor, automatically adding more stretch or tension to the web.

Tube Former and Air Bearing Referring now particularly to FIGS. -12 and 15, the tube former 24 is mounted by right angle brackets 156 to the top of a horizontal platform 158, and overlies a central opening 160 out out of the platform. The filling mandrel is suspended through the tube former and opening 160 to extend below platform 158. Four vertical arms 162, 164, 166 and 168 are rigidly attached to the underside of the platform and extend downward therefrom alongside the filling mandrel. The arms 164 and 166 jointly carry the restraining bar 60, whereas arms 162 and 168 carry the opposite restraining bar 62. The arms 166 and 168 also serve to journably support the gusseting rollers 64 and 66, respectively. A pair of fixed frame arms 152 and 154 provide rigid support for the platform.

The tube former is preferably sheet metal which is formed to define a generally hollow, cylindrical body having overlapped radially spaced, vertical edge portions 170'and 172. The edge portions are bracketed together by an adjustable bracket assembly 174. Assembly 174 allows the tube former to be expanded or contracted circumferentially to permit the making of a slightly larger or smaller tube in response to variances in the bulk density of the product load. The tube former includes plural cut-outs 176 extending upwardly from its lower periphery or edge to give better flexibility to make this adjustment. Also the former is cut back at 180 underneath vertical edge portions 170 and 172 to permit almost immediate access of hot welding gas to the tube.

The top edge 182 of the tube former can be generally near parabolic in shape. However, its exact optimum shape is determined experimentally depending on the thickness and characteristics of web 14. Attached to the top edge of the tube former in the manner of a rim, is a hollow, relatively small diameter tube 184. The

tube includes numerous perforations 186 to provide an air bearing over which the web is floated as it is being drawn through the former. The air bearing is continually fed by a regulated compressed air line 188, and complements fine web tension and registration control by reducing unwanted and uncontrolled friction drag forces, and minimizes any prospect of drag induced damage, breakage, or unrecoverable over-stretching of the web.

Hot Gas Vertical Welder The vertical seam welder 28 is best shown in FIGS. 10, 13 and 14. The seam welder is carried on a horizontal slide 194 which moves transversely on a fixed slideway 196. The slideway is supported off platform 158 by a rigid extension arm 198. An air cylinder 190 is mounted upon slide 194, and the arm 192 of the air cylinder is attached by a rigid bracket 200 to slideway 196. The air cylinder operates slide 194 to move the vertical seam welder to the approximate welding position, hold it there during operation, and automatically retract it to a safe distance when apparatus 10 is stopped to avoid burning the web.

Fine vemier adjustment for the exact welding position or distance from the tube is controlled by use of a vemier slide 202 moveable transversely in a fixed slideway 204 which is attached to slide 194. The Vernier slide is operated by a low speed electric motor 206 affixed by a vertical bracket 208 to the back of slide 194. The motor turns a preferably fine threaded screw 210 through a coupling 212. The screw is threaded into the vernier slide to cause and hold fine adjustments.

The vertical seam welder includes a relatively flat, vertical hot gas welding head or block 214 mounted to the forward end of a horizontal heater barrel 216 through an adapter 218. The opposite end of the heater barrel is attached to a holder 220 which, in turn, is affixed to slide 202. The welding head includes internal diverging baffles 222 to uniformly distribute the incoming gas flow to a narrow vertical slot 224 which applies the gas to the tube. The slot 224 is centered on the longitudinal center line of the overlapped edges of the tube. The heater barrel contains internal calrod gas heating elements (not shown), and receives compressed gas from a pressure regulated line 226. The filling mandrel includes an embedded vertical back-up strip 230, such as of glass impregnated Teflon, aligned with slot 224 to prevent sticking of the tube to the mandrel.

A plate, 232 is attached to the welding head, from which the chilling head 30 is suspended by a pivot connection 234. The chilling head is adjustable for inclination with the vertical axis through means of a curved slot way 236 and tightening nut 238. The chilling head includes a narrow vertical slot 240 aligned vertically with slot 224 of the welding head, and is internally baffled'at 242 to issue a generally uniform column of cooling gas through slot 240. A pressure regulated compressed air line 244 operates the chilling head.

Operation of the Vertical Seam Welder The compressed air line feeding the hot gas block must provide sufficient velocity pressure to cause intimate contact between the interfaces of the overlapped web in order to achieve optimum sealing results. The temperature of the welding gas is balanced with the gas flow rate in order to supply enough BTUs to securely weld the interfaces. If the air is too hot or the gas block too close, non-removable weld wrinkles appear. Under optimum conditions the vertical weld or seam 246 of the tube will initially show wrinkles as depicted in FIG. 16, even after being partially cured by the chiller head. However, when the weld is subjected to the stress of the product load, essentially all wrinkles are removed, and a smooth, virtually invisible weld is achieved, as shown in FIG. 17. If properly formed and chilled, the finished weld line is invisible or near invisible even to close inspection, and shows a virtually complete absence of wrinkling. The chilling head is operated to the benefit of the wrinkling removing effects of the product load stress by not over-curing the weld.

The preferred means of temperature control is through a thermocouple in adapter 218 which signals the off-on operation of the calrod heater elements. A vemier rheostat preferably controls the voltage to the calrod heaters. Once the system is in balance, and the rheostat used to adjust the voltage to the calrods, minimum on-off operation is required, and a constant uniform gas temperature is available for welding.

The Bag Sizing Cage The bag sizing cage is illustrated best in FIGS. 18 and 19. The sizing cage comprises vertical side plates 252 and 254 which are mounted by frame attachments (not shown) in opposed fixed relationship. The side plates jointly carry four rotatable, horizontal shafts 256, 258, 260 and 262, which are arranged rectangularly as viewed from the end. Each shaft carries four axially spaced sprockets 264 of identical size. The shafts 256 and 258 cooperate to mount and convey four side-byside continuous chains 266 to fonn the vertical conveyor assembly 34. The vertical conveyor assembly 36 is formed by shafts 260 and 262, and four side-by-side continuous chains 268. The conveyors are driven in unison by an enclosed gear train 270 connecting between shafts 256 and 260, and a motor 272 which is coupled to the end of shaft 256, and affixed to vertical side plate 254 through a mounting piece 274. A hydraulic motor is preferably employed of a type having independent torque and speed control. The chains 266 and 268 are preferably double pitch, wing type roller chains to which the slats 40 are affixed through spacer elements 276.

A floating vertical pressure plate 278 backs up the inner run of chains 266, and cooperates in a manner to be described, with a fixed vertical rear support plate 280 which backs up the inner run of chains 268. The floating pressure plate is slidably supported on guide pins 282 that are movable in guide bearings 284. The guide bearings, in turn, are fixedly mounted to a front vertical support plate 286. The latter also mounts a plurality of air cylinders 288 which operate the floating pressure plate on guide pins 282. Both the front and rear vertical support plates extend between and are supported by rigid attachment to vertical side plates 252 and 254.

The Sealing Head Assemblies The sealing head assemblies 42 and 44 are illustrated best by FIGS. 20-28.

Referring first to sealing heads 44 (see particularly FIGS. 20-23), the same each comprise and elongated rectangular mold block or holder 294. A plurality of spaced apart arms or trunions 296 are rigidly affixed to the back wall 298 of the mold block. The arms jointly carry a raised mounting shaft 300, which, in turn, is pivotally connected to a back mounting plate 302 through spaced arms or trunions 304 extending normally off the plate. The plate 302 is affixed to roller chains 268 of vertical chain assembly 36 to pivotally mount the molding block thereto with true alignment between the longitudinal axis of the block and the horizontal axis.

Mounted to each end of the mold block is a fixed slideway 310 and 312, respectively. The mold block defines an elongated rectangular cavity 314 which extends between slideways 310 and 312, and is open at the mating face 316 of the mold block. A movable cutter head 318 is contained within cavity 314. The cutter head is attached to slides 320 and 322, operating in slideways 310 and 312, respectively. The slides 320 and 322 each include a roller type cam follower 324 and 326, respectively, which are operated by vertical strip cams 328 and 330 affixed to the rear support plate 280 of the sizing cage. The slide and slideways each include an exhaust port 332 and 334, respectively, which register in the forward cammed position to provide communication between cavity 314 and the atmosphere. A pair of springs 336 connect between each slide and slideway to spring load the cutter head in a retracted rest position.

The cutter head 318 comprises an elongated central knife holding portion 338 defining a narrow slot 340. The slot receives a knife blade or tube parting element or means 342 that is removably secured therein by tightening and loosening set screw assemblies 344. The knife is preferably a scalloped edge, single bevel knife, and is preferably held in the slot at a slight grade over the length thereof, to achieve a scissor-type cutting effect. On each side of the knife holding portion are an aligned series of exhaust ports 346 separated by lands 348. The lands give rigidity to the knife holding portion. The exhaust ports provide communication between the face 350 of the cutter head and the registrable exhaust ports 332 and 334 in the slides and slideways. A raised welding detent 352 is disposed between the terminating longitudinal edges 354 of the cutter head and the exhaust ports 346 on each side of knife blade 342. The face of each detent 352 comprises a backup welding surface, the operative or effective portion-of which is spaced from the portions of the tube under clamping pressure, for reasons as will become evident hereinafter.

Referring now particularly to FIGS. 24-26 the sealing heads 42 are in part similar to scaling heads 44. Each include an elongated mold block or holder 360 affixed pivotally to a mounting plate 362 through a shaft 364 and trunions 366 and 368, respectively. The plate, in turn, is affixed in horizontally level fashion to the roller chains of vertical conveyor assembly 34.

A hot gas inlet valve 370 is affixed to one end of mold block 360. The inlet valve includes a raised center post 372 which is elevated above the top wall 374 of the mold block (in reference to the orientation of the mold block as it travels through the sizing cage). At the opposite end of the mold block is a cold gas inlet valve 376 which is identical to valve 370 except that it is reversely oriented so that the center post 378 thereof is offset beyond the bottom wall 380 of the mold block. The center post of each valve is slidably carried in a hollow valve body 382. Each valve is operated by depressing the center post against a spring 384, to unseat a valving head 386 from an internal valving seat 388.

Each valve includes an external valving seat 390 about file center post thereof, for seating the valves against hot and cold gas delivery heads, respectively, as will be described.

The mold block 360 defines an elongated open ended cavity 392. A hollow welding head 394 is inset fixedly in cavity 392 and extends between the hot and cold gas inlet valves 370 and 376. The welding head includes a welding face 396 elevated from the floor of the cavity to define a continuous channel 398. Each valve body 382 communicates with channel 398 through a passageway 400.

The welding face 396 includes an elongated, vertical knife receiving well or slot 402. The knife receiving well is bordered on each side by elongated strips 404 of resilient, high heat withstanding material, which provides a raised back-up surface for cutting.

Extending alongside each strip 404, but spaced therefrom, is a narrow, near continuous slot or stream forming opening or means 406. Narrow lands 408 interrupt and support the slots against possible warpage under high temperature welding conditions. The slots provide communication between channel 398 and welding face 396 for directing the welding and cooling gases as will be explained hereinafter. The floor of the cavity underneath the welding head is lined with a flat heat shield covering 410 such as of Teflon. A sealing gasket 412 of relatively high heat withstanding material is peripherally continuous about welding face 396 and is interposed between the sidewalls of the cavity and the welding head. The gasket 412 is raised from the welding face to form a welding space or chamber upon mating of sealing heads 42 and 44 (see FIG. 28), in which the tube is essentially free of mechanical clamping pressures.

The Engagement and Operation of the Sealing Heads The angle of approach of the sealing heads as they enter the sizing cage is adjustable by set screws 420 attached to each mounting plate 302 and 362. This adjustment is held by springs 422 attached between the mounting plate and the back of mold blocks 294 and 360, respectively. The angle of approach is set so that the sealing heads smoothly roll together and mesh properly (see FIGS. 27 and 28). The sealing heads 44 each mount a set of four over and under guide rollers 424, respectively, through bracket attachments 426. The guide rollers assist to keep register between the sealing heads in the clamped position by engaging fixed locking strips 428 on the bottom wall 380 of the opposite sealing head 42, and fixed break-away brackets 430 on the top wall 374 thereof. The break-away brackets particularly will prevent the sealing head 42 from slipping ahead of the sealing head 44, at the moment the same begin to part or disengage at the bottom of the sizing cage.

The clamping pressure between the sealing heads is controlled by the floating pressure plate 278 with the assistance of rear support plate 280, through regulating the line pressure to air cylinders 288 at the back of the pressure plate. The clamping pressure firmly seats sealing gasket 412 against the mating face of mold block 294, forming an essentially gas tight seal therewith, along opposed clamping zones or areas that extend transversely across the width of the tube, and which are separated in the longitudinal direction, to define the upper and lower limits of the welding chamber.

Almost simultaneously with the clamping of the film between the sealing heads, the cam rollers on slides 320 and 322 engage strip cams 328 and 330, respectively. The slides force the cutter head forward on slideways 310 and 312, causing knife 342 to cut or part the tubing at welding face 396. The detents on the cutter head draw the parted edges or cut ends 432 and 434 of the tube away from the knife well as the knife moves to the extreme forward position, thereby separating and defining a space between the cut ends which communicates with exhaust ports 346.

At this moment, a moving hot gas supply head 436 moves vertically down upon the hot gas inlet valve 370, seating with the valve and depressing the center post to force a heated-welding gas, such as air into channel 398. The operation and structure of the assembly supplying heated gas (and also the assembly supplying cooling gas in the latter part of the weld forming cycle) is described in some detail hereinafter.

The hot gas introduced into channel 398 escapes at high velocity-through the directional slots 406, preferentially striking an extreme portion of the cut ends, remote from the clamped areas or zones, and then venting from the welding chamber through the exhaust ports 346 on each side of the knife, and eventually to the atmosphere through the ports 332 and 334 which register in the forward cammed position. The high velocity directional flow of the hot gas causes the cut plastic ends to lay down smoothly against detents 352 by fluid or velocity pressure to intimately contact all interfaces of thecut ends. Outwardly of the detents, dead spaces or buffer areas 438 are defined in the welding chamber that are removed from the primary flow of the heated gas streams. Retarded heat transfer and flow conditions exist in dead spaces to selectively prevent heat deformation temperatures to extend to areas of the tube under clamping pressure.

The cut ends, due to the directionality and flow of the hot gas streams are bathed in hot gas to a molten or near molten condition. The thinning of the cut ends is only a function of velocity pressure since the cut ends are not mechanically restrained. The velocity pressure of the welding stream is sufficient to intimately hold the layers of the cut ends together to form a strong bond between all interfaces as sealing or welding temperatures are reached. Too much velocity pressure can wash out the cut ends, causing undesirable thinning. Most optimally, therefore, the velocity pressure is sufficient to hold the intimate contact between the welding faces, but not so, high as to thin and wash out the cut ends, and the temperature of the hot gas stream is controlled to provide sufficient BTUs of heat to form a strong weld at all interfaces. If velocity pressure is correct, the welds can be formed showing virtually no thinning throughout the entire extent thereof. Under proper welding conditions the unrestrained cut edges tend to shrink back to form a thickened or swollen weld of remarkably tough quality.

In order to provide a uniformly strong weld across the tube, the hot gas welding stream must flow at essentially uniform velocity over the length of the directional slots. This is achieved by designing the cross-sectional area of channel 398 to be greater by a certain factor than the combined cross-sectional area of the directional slots. in an experimental shop apparatus, using a welding head 394 as illustrated herein, the most restricted cross-sectional area of this chamber was designed to be approximately four times the area of the 

1. Apparatus adapted particularly for forming industrial size bags from continuous thermally sealable web materials, and for simultaneously filling and sealing the bags in-line as they are formed, said apparatus comprising: a hollow tube former for converting the web into an upwardly open vertical tube having its marginal edges overlapped, a filling mandrel suspended downwardly generally centrally through the tube former for communication with the interior of the tube, means to integrally join together the overlapped marginal edges of the tube, at least one pair of co-acting sealing heads, means to move the sealing heads to periodically grasp the tubing across the transverse extent thereof, and to draw the tubing downwardly from the filling mandrel, the sealing heads being adapted to clamp the tube by mechanical pressure to form a temporary bottom, means to dump a product load through the filling mandrel and into the tube subsequent to the formation of each such temporary bottom, means to introduce heated welding gas to the sealing heads, the sealing heads including means to transversely part the tube, and to apply the heated gas generally preferentially to the parted edges thereof, said sealing heads together defining a welding space in which the parted edges are free from mechanical clamping restraint, said welding space including areas of retarded heat transfer conditions residing intermediate said parted edges, respectively, and the portions of the tube under mechanical clamping pressure by the sealing heads, said areas of retarded heat transfer conditions being adapted to prevent the clamped areas of the tube from reaching heat deformation temperatures.
 2. The apparatus as recited in claim 1 including means to inwardly tuck opposite sides of the tube in a sequence prior to each clamping engagement of the sealing heads to produce side gusseted bags.
 3. The apparatus as recited in claim 2 including means to apply the heated gas streams at a velocity that is generally uniform across the transverse extent of said edges.
 4. The apparatus as recited in claim 1 wherein the apparatus includes means to sequentially introduce pressurized heated and then cooling gas to the sealing heads and stream forming means to apply the gas as High velocity streams to the parted edges, to form the seals, and thereafter, to generally immediately cool the seals by application of cooling gas thereto, prior to release of the clamping pressure.
 5. The apparatus as recited in claim 4 wherein pressurized heated and cooling gas is sequentially introduced into a common chamber defined in one of said sealing heads, said chamber being in communication with said welding space through said stream forming means.
 6. The apparatus as recited in claim 5 wherein said stream forming means comprise elongated transversely extending slot means of narrow width, adapted in combination with the internal size of said chamber, to form streams that impinge upon said parted edges at a velocity that is generally uniform across the transverse extent of said edges.
 7. Apparatus adapted particularly for forming industrial size bags from continuous thermally sealable web materials, and for simultaneously filling and sealing the bags in-line as they are formed, said apparatus comprising: a tube former for converting the web into an upwardly open vertical tube having its marginal edges juxtaposed, means to integrally join together the marginal edges of the tube, a filling mandrel suspended downwardly generally centrally through the tube former for communication with the interior of the tube, means to periodically introduce a product load into the tube through the filling mandrel, at least one pair of co-acting sealing heads, means to move the sealing heads to periodically grasp the tubing across the transverse extent thereof, the sealing heads being adapted to firmly clamp the tube by mechanical pressure, means to provide pressurized heated gas, the sealing heads including means to transversely part the tube, and to apply the heated gas generally preferentially to the parted edges thereof, said sealing heads together defining a welding space in which the parted edges are free from mechanical clamping restraint, said welding space including areas of retarded heat transfer conditions residing intermediate said parted edges, respectively, and the portions of the tube under mechanical clamping pressure by the sealing heads, said areas of retarded heat transfer conditions being adapted to provide buffer areas which impart resistance to heat induced thinning of the areas of the tube which are under clamping pressure.
 8. The apparatus as recited in claim 7 wherein said sealing heads define first and second transversely extending back-up surface means, having operative portions which are remote from the areas of the tube under clamping pressure, to thereby define buffer areas located intermediate the operative portions of the first and second back-up surface means, respectively, and said clamped areas, an evacuation passage means defined between said first and second back-up surface means for venting the heated gas, the gas applying means comprising means to form high velocity gas streams directed to flow preferentially against said operative portions, respectively, and thereafter be vented through said evacuation passage means.
 9. The apparatus as recited in claim 8 wherein the operative portions of said back-up surface means are raised and present a generally rounded face against which the seals are formed by the impinging gas streams.
 10. The apparatus as recited in claim 8, wherein the apparatus includes means to sequentially provide pressurized heated and then cooling gas, stream forming means in at least one of the sealing heads to apply the gas as high velocity streams to the parted edges, to form the seals, and thereafter, to generally immediately cool the seals by application of cooling gas thereto, prior to release of the clamping pressure.
 11. The apparatus as recited in claim 7 wherein the sealing heads define a first back-up surface means above said parting means, a second back-up surface means below said parting means, a first buffer area defined above said first back-up surface means, a second buffer area defined below saId second back-up surface means, an evacuation passage means defined between said first and second back-up surface means, means to convert pressurized heated gas into high velocity streams directed to preferentially avoid said buffer areas and impinge upon said first and second back-up surface means, respectively, and be removed through the evacuation passage means.
 12. The apparatus as recited in claim 11 wherein said means for converting pressurized heated gas into high velocity streams, provides streams which impinge upon the parted edges, respectively, at a velocity that is generally uniform across the transverse extent of said edges.
 13. The apparatus as recited in claim 7, wherein said apparatus includes means to sequentially provide pressurized heated and then cooling gas, stream forming means in at least one of the sealing heads to apply the gas as high velocity streams to the parted edges, to form the seals, and thereafter to cool the seals by application of cooling gas thereto, prior to release of the clamping pressure.
 14. In apparatus for providing a flexible, generally vertical tube from thermally sealable material simultaneously with the periodic filling of the tube, and the collapsing and traverse sealing of the tube at spaced intervals to form therefrom filled bags, the combination which includes: a hollow filling mandrel about which the tube is formed, filling means to periodically introduce a product load into the tube, through the filling mandrel, means to periodically clamp the tube underneath the filling mandrel to draw the tube downwardly to provide a product receiving space for the product load, means within the clamping means to define a welding space in which the tube of mechanical clamping pressures, means to transversely part the tube in the welding space, along a line remote from the clamped portions of the tube, means operative in the clamped position to urge the plies of the parted edges into generally intimate sealing contact across the transverse extent thereof by velocity pressure, through applying high velocity gas streams to the parted edges, means to heat the gas streams to seal the parted edges at least partially by the heat contained in said streams, said urging being adapted to direct the heated gas streams preferentially upon the parted edges, respectively, at areas thereof remote from the areas of the tube under clamping pressure, means in communication with the space between said parted edges, and adapted to vent the heated gas streams from the welding space after such preferential impingement thereof against the parted edges.
 15. The apparatus as recited in claim 14 including means, sequentially operational after the application of the heated gas streams, to form and apply high velocity streams of cooling gas to the parted edges prior to release of the clamping pressure.
 16. The apparatus as recited in claim 15, wherein the heated and cooling gas streams sequentially issue from common stream forming opening and impinge directly therefrom upon the parted edges.
 17. The apparatus as recited in claim 14 wherein said means to urge the plies of the parted edges into generally intimate contact, is adapted to impart a velocity pressure to such edges which is generally uniform across the transverse extent of such edges.
 18. The apparatus as recited in claim 17 including means to inwardly tuck opposite sides of the tube prior to clamping the tube to form side gusseted bags.
 19. The apparatus as recited in claim 14 wherein the means to urge the plies of the parted edges into generally intimate contact, applies the streams diagonally with respect to the vertical plane, such that the streams flow diagonally toward the extreme portions, respectively, of the parted edges.
 20. In apparatus for providing a flexible, generally vertical tube from thermally sealable material simultaneously with the periodic filling of the tube, and the collapsing and transverse sealing of the tube at spaced intervals to form therefrom filled bags, the combination which includes: means to clamp the tube across its width along upper and lower zones spaced in the longitudinal direction, means to part the tube between and remote from the clamped zones, means to separate the parted edges to define a space therebetween, first and second back-up surface means defining transversely extending operative portions spaced from the clamping zones in the vertical direction, means to urge the plies of the parted edges into intimate sealing contact across their transverse extent by fluid pressure applied in the form of high velocity gas streams to one side thereof and acting against the operative portions of said first and second back-up surface means, passage means defined between the operative portions of said first and second back-up surface means, and adapted for communication with the space between the parted edges, for venting said gas streams, means to heat said gas streams, and means sequentially operative after the heating means to positively cool the parted edges prior to releasing the clamping pressure.
 21. The apparatus as recited in claim 20 wherein the cooling means comprise means to apply high velocity streams of cooling gas to the vicinity of the operative portions of the first and second back-up surface means.
 22. The apparatus as recited in claim 21 wherein pressurized heated and cooling gas is introduced to common stream forming means, and directed thereby to the vicinity of operative portions of said back-up surface means.
 23. The apparatus as recited in claim 20 wherein the areas defined between the operative portions of said first and second back-up surface means, respectively, and the upper and lower clamped zones, are removed from the primary flow of the heated gas streams, and are thereby adapted to provide buffer zones that resist the transfer of heat deformation temperatures to the portions of the tube under clamping pressure.
 24. The apparatus as recited in claim 23 wherein said operative portions of the first and second back-up surface means are raised, said buffer areas being partially recessed behind said raised operative portions.
 25. The apparatus as recited in claim 24 wherein said operative portions present a generally rounded back-up face.
 26. The apparatus as recited in claim 20 wherein said urging means is adapted to apply a velocity pressure to the parted edges which is generally uniform across the transverse extent of said edges.
 27. The apparatus as recited in claim 26 including means to inwardly tuck opposite side portions of the tube, prior to each clamping step, to produce side gusseted bags.
 28. The apparatus as recited in claim 20 wherein the urging means is adapted to apply the streams diagonally inwardly with general directionality being toward the space defined between the parted edges.
 29. The apparatus as recited in claim 20 wherein the operative portion of said first and second back-up surface means, are adapted to contact said parted edges, respectively, and physically urge said edges apart to provide said separating means.
 30. In apparatus for providing a flexible tube from thermally sealable material, simultaneously with the periodic filling of the tube, and the collapsing and traverse sealing of the tube at spaced intervals to form therefrom filled bags, the combination which includes: means to form an essentially gas tight clamp on the tube across its width along first and second zones spaced in the longitudinal direction, means to part the tube between and remote from the clamped zones, first and second back-up surface means, defining transversely extending operative portions spaced from the clamping zones in the longitudinal direction, means to urge the plies of the parted edges into intimate sealing contact by fluid pressure applied to one side thereof and acting against the operative portions of said first and second back-up surfaces, means to heat the areas of the parted edges acted upon by the urging means to sealing temperatures, and mEans sequentially operative after the heating means to positively cool the parted edges prior to releasing the clamping pressure.
 31. The apparatus as recited in claim 30, wherein said apparatus includes means to separate the parted edges to define a space therebetween, a venting passage means between said operative portions and in communication with said space, means to sequentially provide pressurized heated and then cooling gas, stream forming means to apply the gas as high velocity streams to the parted edges, to form the seals, and thereafter to cool the seals by application of cooling gas thereto, prior to release of the clamping pressure.
 32. Form, fill and seal apparatus adapted for the production of filled industrial size bags and comprising: a. a hollow filling mandrel about which the material is formed as a tube, and means for periodically delivering a pre-measured product load through the filling mandrel and into the tube; b. means to clamp the tube, prior to each dump made by the filling means, along first and second zones which are spaced in the longitudinal direction, and extend transversely across the width of the tube; c. means, operative in the clamped position, to transversely part the tube along a line extending between and remote from said clamped zones, means to seal the transverse edge portion, that is defined above the part line, to form the bottom seal on the bag next to be filled, means to simultaneously seal the transverse edge portion, that is defined below the part line, to form the top seal on the bag last filled, said sealing means comprising: d. back-up means located in the space between said clamped zones, means to sequentially supply pressurized, heated gas, and thereafter pressurized cooling gas, means to convert such pressurized gas into high velocity streams that impinge against said parted edges, respectively, to cause said edges to lay down against said back-up means by velocity pressure, and to be sealed by the heat contained in said streams, and thereafter to be cooled prior to releasing the clamping pressure, and means adapted to selectively maintain areas of the tube, immediately adjacent the clamped zones, sufficiently cool to resist objectionable heat induced thinning of the portions of the tube under clamping pressure. 